Thermostatic valves are used in general to regulate coolant flow for internal combustion engines. These thermostatic valves are typically electrically heatable valves, the working point of which at the setpoint temperature may be varied using engine management as a function of the operating point of the internal combustion engine.
Control valves are currently under development which include valve elements designed as flat slide-valves, e.g., rotating disks, which are rotated using an electric drive, and which close or open or partially close and partially open—in a manner that is a function of the operating point and depends on the temperature of the internal combustion engine—corresponding flow cross-sections so that coolant may flow into a radiator or a bypass.
To minimize costs, it has proven advantageous to use a DC motor. This motor is unsuitable for use, however, as a wet-rotor motor in a water-glycol mixture which is typically present in coolants, thereby making it necessary to provide a shaft passage from an inner wet region into an outer dry region. The shaft passage is sealed off with seals, the service lives of which are usually shortened by the coolant which may potentially contain particles, e.g., moulding sand particles and the like. Elastomer-based shaft seals are therefore unsuitable. Elastomer-based shaft seals do not have the seal integrity required for the necessary service life.
Slide-ring seals may be used without a problem with media that contain particles, e.g., water-glycol mixtures which may contain particles of moulding sand, but they have the disadvantage of resulting in a significant increase in friction. A greater amount of torque is required due to the significant increase in friction at the drive shaft and, therefore, greater torque must be provided by the electric drive. This results in a significant increase in the dimensioning of the electric drive, however.
As an alternative, a concept based on a wet-running EC motor is being discussed at this time. It would definitely require electronic engine management, however. This electronic engine management makes the system considerably more expensive, however, and makes it necessary to use additional connector pins.
DE 10 2005 056 763 A1 relates to a device for controlling transmission control couplings, with which slide-valve cylinders are used. A pressure control valve for hydraulic systems, in particular automatic vehicle transmissions, is described, in the case of which a drive is provided to actuate the pressure control valve. The pressure control valve includes a valve housing into which the following empty: an inlet with inlet pressure pZ, an outlet with outlet pressure pA, and a control channel with a system pressure p. A slide-valve cylinder is provided in order to connect or separate the inlet and outlet and the control channel from one another. According to the solution described in DE 10 2005 056 763 A1, the slide-valve cylinder is driven by a stepper motor. The slide-valve cylinder is located in the cylinder housing, and at least one flat slide-valve cylinder segment is formed on this at least one slide-valve cylinder.
Magnetic couplings may be used in addition to the systems described above, which are driven via electric motors, either by a DC motor or a wet-running EC motor.